Abraham Metz.

The anatomy and histology of the human eye online

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126



THE ANATOMY AND HISTOLOGY



cavernous sinus, on the inner side of the anterior clinoid pro-
cess, and enters the orbit through the optic foramen, below
(a, Fig. 61, left hand) and on the outer side (b) of the optic
nerve. It then crosses over the nerve to the inner side (c),



FIG. 61.




Arteries of the eye. left-hand figure ; veins, right-hand figure. (From Pilz.)

leaves the muscle-cone, passes beneath the musculus obliquus
superior, to the inner wall of the orbit, forward (d), to the
inner angle of the eye, where it divides into two terminal
branches, the arteria frontalis, and the arteria dorsalis nasi.
The first branch given off from the ophthalmic is the arteria
lachrymalis (), which arises near the optic foramen, and accom-
panies the lachrymal nerve along the upper border of the
external rectus muscle, and is distributed to the lachrymal
gland. The terminal branches that escape from the gland are
distributed to the upper lid and to the conjunctiva, and anas-
tomose with the arteria palpebralis.

The lachrymal artery gives off one or two malar branches,



OF THE HUMAN EYE. 127

one of which, passes to the temporal fossa, through a foramen
in the malar bone, and anastomoses with the deep temporal
arteries. The other passes to the cheek to anastomose with
the arteria transversa faciei. The next branch given off from
the ophthalmic is the largest, the arteria supraorbitalis (s), and
is given off above the optic nerve. It passes forward with the
frontal nerve, and passes above the muscles, between the
levator palpebrce and the periorbita ; passing through the foramen
supraorbitale, it divides into a superficial and a deep branch,
which supply the muscles and the integument of the forehead,
and the pericranium, and anastomose with the arteria tem-
poralis, the angular branch of the arteria faciei, and the artery
of the opposite side.

The arteria ethmoidalis anterior (x) et posterior (w) are given
off at the point where the ophthalmic artery reaches the inner
wall of the orbit (d). The former accompanies the nasal
nerve through the anterior ethmoidal foramen, supplies the
anterior ethmoidal cells and frontal sinuses, enters the cranium,
and divides into a meningeal branch, to supply the dura mater,
and a nasal branch, which passes through an aperture in the
cribriform plate into the nose.

The arteria palpebralis superior et inferior arise opposite the
trochlea, from the arteria opldhalmica, encircle the eyelids near
their free margin, between the tarsal cartilage and the muscu-
lus orbicularis; they form free anastomoses, as with the infra-
orbital artery, and with the orbital branch of the temporal
artery, and send off a twig to ramify on the nasal duct.

The arteria frontalis, one of the terminal branches of the
arteria ophthalmica, passes from the orbit at its inner angle to
be distributed to the muscles and integument of the forehead,
and anastomoses with the arteria supraorbitalis.

The arteria nasalis, the other terminal branch of the arteria
ophthalmica, passes from the orbit above the tendo-oculi, gives
off a branch to the saccus lachrymalis, divides into two branches,
which anastomose with the arteria angularis, and sends a branch
to supply the surface of the nose, the arteria dorsalis nasi.



128 THE ANATOMY AND HISTOLOGY

The arterice ciliares, are divided into arterice ciliares breves,
arterice ciliares posterior longce, et arterice, ciliares anticce.

The arterice ciliares breves are from twelve to fifteen in num-
ber, arise from the arteria ophthalmica, or its branches, and
penetrate the sclerotica around the optic nerve, to supply the
choroid, as heretofore explained.

The arterice ciliares longce, two in number, perforate the
sclerotica on the inner and outer sides of the optic nerve
entrance, to supply the ciliary body and the iris, as explained
in the description of the choroidea.

The arterice ciliares anticce are a number of muscular branches
that penetrate the sclerotica, close to the corneal border, and
send branches to the ciliary body and the great arterial circle
of the iris.

The arteria centralis retinal, the smallest branch given off
from the arteria ophthalmica, penetrates the optic nerve near
the sclerotica, and passes along the axis of the nerve into the
eye, to be distributed, as elsewhere described.

There are two muscular branches, a superior and an inferior,
which supply the muscles of the eyeball. The superior supplies
the levator palpebrce, rectus superior, and the obliquus superior.
The inferior branch supplies the external and inferior recti and
obliquus inferior. This branch furnishes most of the anterior
ciliary arteries. These branches expand beneath Tenon's mem-
brane, and will be more minutely described after the descrip-
tion of the veins of the orbit.

The Veins.

The vena ophthalmica, in its branches, is very similar to the
arteria ophthalmica (Fig. 61, right hand figure). It begins at
the inner angle of the eye, where it anastomoses with the
anterior facial vein (d), and which collects the vena frontalis (a),
the vena dorsalis narium (b), and the vena supraciliares (<?). It
proceeds backward along the inner wall of the orbit, enters
the cavity formed by the ocular muscles, but does not pass out



OF THE HUMAN EYE. 129

through the foramen opticum, but through the Jlssura orbitalis
superior into the cranial cavity, and empties itself into the
sinus cavernosus.

Outside of the muscular pyramid, the vena ophthalmica is
joined by the vence palpebralis (/) and the vena sacci lacry-
malis ; and inside of the muscular cone it is joined by the
veins from the muscles (A, A, i, m, w), which are ordinarily
joined, immediately behind the corneal border, by the anterior
ciliary veins. It is also joined by 4 to 6 branches of the vasa
vorticosa (#, k\ and a few branches of the posterior ciliary
veins, which Leber correctly asserts have their origin only in
the sclerotica. It is said in the text-books that there are two
long posterior ciliary veins corresponding to the long ciliary
arteries. Leber asserts that they cannot be found in the eye;
which coincides with the observations of the author. It is
also joined by the vena glandulce lacrymalis (7, 1) and vena cen-
tralis retinae, also by the vena supraorbitaria (p) ; which receive
some branches from the ocular muscles ; and sometimes this
vein enters the cavernous sinus singly.

The sclerotica receives its supply of blood from the posterior
and anterior ciliary arteries ; and the veins carrying off the
blood have been described above. The small vessels form on
the sclerotica a vascular network of large meshes, which have
the peculiarity, that almost every arterial branch has a vein
accompanying it on each side. The veins anastomose much
more frequently than the arteries. The larger branches of
the arteries are tortuous in their course. From this network
of vessels a fine network of capillaries originates. Those de-
rived from the straight muscles, the anterior ciliary arteries,
pass through the tendons of the muscles. The branches of
the scleral network derived from the anterior ciliary arteries,
anastomose with the posterior network derived from the pos-
terior ciliary arteries.

As far as the sclerotica is covered by the conjunctiva we
must distinguish its vessels from the deep layer of the anterior
ciliary vessels. Both are at their periphery wholly isolated,



130 THE ANATOMY AND HIS'TOLOGY

as the conjunctiva derives its vessels from the superior and
inferior palpebral and the lachrymal arteries. It is only near
the corneal border where the union between the two systems
of vessels begins, and at this point the ciliary vessels send out
numerous vascular loops to anastomose with those of the con-
junctiva, which run backward in a radiary manner, and supply
the innermost zone of the sclerotical conjunctiva with twigs
for a distance of 2 to 3 mm. The looped network which over-
laps the border of the cornea is also derived from branches of
the anterior ciliary arteries.

The anterior ciliary arteries pass through the tendons of the
muscles to the surface of the sclerotica, generally two branches
to a muscle (one to the rectus externus), and run in a very tor-
tuous manner toward the corneal border, where they send
branches to the sclerotical capillary network ; but by far the
larger proportion of branches penetrate the sclerotica in a
manner elsewhere described. The branches given off to the
capillary network of the sclerotica are very fine, and most of
them are given off from the anterior ciliary arteries, as they
run on the surface of the sclerotica ; a small number, how-
ever, proceed from the branches penetrating into the sclerotica.

Nearer to the corneal border their terminal branches, and
sometimes also some of the larger branches, bend laterally,
and ibrm bow-shaped connections with each other, and from
which new branches are given off and proceed forward and
outward. From these bow-shaped communications proceed
the vascular loops which pass into the conjunctiva, in the
annulus conjunctive, which are the direct communication be-
tween the vessels of the sclerotica and the conjunctiva ; also
the branches are given off which form the looped vascular
network at the border of the cornea. The former exist in
the annulus conjunctive, side by side, at a distance of \ to J
millimetre; at first 'they run a short distance forward, bend
outward in a bow-shaped manner, and reach the conjunctiva,
in which they run for some distance directly backward, send
off some twigs, and unite with the arteries coming from the



OF THE HUMAN EYE. 131

periphery of the conjunctiva. The looped network of the
cornea is supplied by the terminal branches of the ciliary
arteries. They run forward on the sclerotica in a straight
manner, and by continual dichotomous divisions, and free
anastomoses, form a rather large-meshed and sharp-angled
vascular network, characterized by its great fineness. It
overlaps the border of the cornea to a distance varying with
the breadth of the limbus conjunctivce, being broader above and
below than on the inside and outside. Its terminal branches
bend over in a curved manner, and pass over into the com-
mencement of the veins, when they become wider, the venous
arm of the angle being at least double that of the arterial.
The looped vascular network of the corneal border also pre-
sents a very complicated capillary network (the veins of which
pass into the anterior ciliary veins), which is only indirectly
connected with the vessels of the conjunctiva. The anterior
ciliary veins are ordinarily more numerous than the arteries,
are less tortuous in their course, anastomose more freely, but
in their general course they are analogous to the arteries.
They collect the veins from the vascular network of the cor-
neal border, from the capillary network of the sclerotica, from
within the globe, from the ciliary plexus and ciliary muscles,
and from the vessels forming the connecting loops of the con-
junctiva. The veins proceeding from the looped vascular
network of the corneal border form a network of polygonal
meshes, which extends backward on the sclerotica, and forms
a zone of 2'" to 3 /r/ in breadth, around the corneal border.
This is generally called the episderal venous network, as it
rests on the sclerotica. This is, during life, much injected
during intra-ocular inflammation. The veins of the conjunc-
tiva, collecting the blood by the anterior ciliary veins, have
the same direction as those described above as coming from
the connecting vascular loops. Like those, they are located
in the annulus conjunctivas, and pass in a looped or sling-like
manner to the conjunctiva, on which they run back to form
connections with the peripheral conjunctiva! veins.



132



THE ANATOMY AND HISTOLOGY



FIG. 62.




tar.




No. 3.




No. 4.



No. 5.





OF THE HUMAN EYE. 133

No. 6. No. 7.





EXPLANATION OF THE FIGURES.
No. 1. Right Eye. Anterior ciliary arteries of a man aged 37 years.

Sup. Superior, very deeply situated, with four perforating-points, p, p, p, p.

INF. Inferior superficial, also having four perforating points.

INT. Internal, 1, with the inferior ramus 1' hidden in %, under a pinguecula ; 2,

very fine branches go out separately from the right inner muscle.

No. 2. Left Eye. Anterior ciliary arteries of a man aged 37 years. (Signification of
figures and letters same as above.)

c. Anastomoses between the external and superior external branches, with perfor-
ating points, p, p, p.

x. One of the internal branches, which seems to terminate in an episcleral vessel.
INT. Internal, with its main tract very sinuous.

No. 3. Sketch of the vessels on the inferior portion of the external part of the eye.
c. Cornea.

a, , a. Conjunctival vessels, being clear red, movable.

', a'. Conjunctival vessels proceeding from the palpebral conjunctiva.
a", a". Anterior Conjunctival vessels, of which a branch forms an anastomosis
with an episcleral vessel at d'.

b, An episcleral vessel, connected by a loop with b 2.
b'. An episcleral vessel, with arborescent ramifications.
b". A deep-seated vessel, going out of the sclerotica.
b'" '. Episcleral network.

3, 3. Fine network surrounding and covering the border of the cornea.

c, c. Anterior ciliary arteries perforating the sclerotica at p, p, p.
c'. A perforating artery situated in the conjunctiva.

No. 4. Anterior ciliary arteries of a boy 13 years old.

SOP. Superior, 1, internal, very small, proceeding perhaps from 2, the middle

dividing in three branches, and anastomosing at c with 3, the external.
EXT. External, a very fine trunk.

INF. Inferior, 1 the internal, after a sinuous course returns to 2, the external ;
this last, toward the point of junction, c, is situated in the conjunctiva, is
rectilinear, and of clear red color.
INT. Internal. 1, the superior ; 2, the inferior ; p, p, p, points where the arteries

disappear in the sclerotica.
No. 5. Conjunctival vessels.
a, a. Posterior.

a", a". Anterior, which near the cornea is bent partly into an episcleral vessel.
No. 6. Episcleral vessels.

3, b. Forming a loop.

b'. Arborescent.

a. A vessel situated in the conjunctiva, and communicating with the episclerai

vessels b.

No. 7. Episcleral vessels dilated by friction.
b', b'. Forming a loop.
3. Fine network around the cornea. (From Danders.)



134 THE ANATOMY AND HISTOLOGY

The arteries that supply the peripheral part of the conjunc-
tiva are the superior and inferior palpebral and the lachrymal.
In a similar arrangement the veins form an arborescent net-
work of irregular meshes.

The above observations on the vessels of the sclerotica and
the sclerotical conjunctiva, from Leber, and based on observa-
tions made on dead eyes, finely injected, are mainly substan-
tiated by the observations of Van Woerden and by Bonders,
on living eyes, by means of the microscope of Amici, adapted
to that of Liebreich. Yan Woerden calls those vessels of the
conjunctiva which surround the border of the cornea, the ante-
rior conjunctival vessels, in contradistinction to the posterior
conjunctival vessels, which have their origin from the palpebral
vessels. In the peripheral part of the conjunctiva there is
but little communication between the conjunctival and ciliary
vessels. This communication becomes more free toward the
border of the cornea, and in the limbus conjunctiva the fine
vessels pass over into the conjunctiva freely in the manner
above described. It follows that in the neighborhood of the
cornenl border the conjunctiva is supplied from the anterior
ciliary arteries, and that under certain conditions the conjunc-
tival vessels may receive blood from, or carry it to, the intra-
ocular circulation. Donders says that the vessels of the interior
of the eye, arteries, and veins, communicate with those of the
exterior, not excluding those of the conjunctiva.

Nerves of the Eye.

The second pair of cranial nerves, the nervus opticus, being a
nerve of special sense, has been described above.

The ganglion ciliare (Fig. 63, k] is a small quadrangular,
flattened ganglion, about the size of a pin's head (Gray) ; is
surrounded by fat ; about 2 r// long, in the middle about O r// .9,
and at the anterior and posterior ends about 0' /r .78 broad. It
lies on the outer and underside of the nervus opticus, about
3J"' in front of the foramen opticum, and about 8'" to 9'"
behind the posterior pole of the sclerotica. Posteriorly, it is



OF THE HUMAN EYE.



135



in contact with the inferior ramus of the nervus oculo-motorius
(s, Fig. 63), and covers the branch of the same nerve that pro-
ceeds to the musculi obliquus and rectus inferior (b, Fig. 63) ;
externally, it is in relation with the musculus rectus externus
at the point where the nervus abducens enters it. This ciliary
(ophthalmic, lenticular) ganglion is located at the point of union
of three nerves, of the ramus naso-ciliaris of the first branch
of the nervus trigeminis (A, Fig. 63), one branch of the oculo-
motorius (d), and one branch of the nervus sympathicus (r).
The branch passing from the trigeminus to the ciliary nerves



FIG. 63.




proceeds from the nervus naso-ciliaris (g] of the ramus primus
trigemini ( U), and the ramus secundus of this nerve also sends a
fibre from the ganglion spheno-palatinum to the ganglion ciliare.
It also sends off, after having passed through the fissura orbi-
talis superior, two branches, the radix longa ganglii ciliaris (h)
and the nervus ciliares longus (), the latter of which some-
times is double. The former is 3"' to 4 r// long, and is found



136 THE ANATOMY AND HISTOLOGY

on the inner side of the nervus naso-ciliaris (g\ and is covered
by the origin of the levator and rectus superior muscles (K\
and also by the ramus superior nervi oculo-motorii, and enters
the outer and posterior corner of the ganglion ciliare (k). The
nervus ciliaris longus, at the point where the nervus naso-
ciliaris (g] runs above the nervus opticus (X), is given off
about 4 r// higher up than the radix brevis from the naso-
ciliaris, turns outward, and lies here on the outer surface of
the nervus opticus. After running along about 3J'", a few
filaments coming from the ciliary ganglion unite with it.

From hence the nervus naso-ciliaris proceeds to the upper
border of the musculus rectus internus (H), and passes out of
the hollow cone formed by the muscles, runs along between
the above muscle and the musculus obliquus inferior (E) along
the inner wall of the orbit, and sends off through the foramen
ethmoidalis anterius the nervus ethmoidalis seu nasalis anterior,
and ends as the nervus infra-trochlearis at the inner angle of
the eye, where it divides into the ramulus ad saccum lachry-
malum, rami conjunctive palpebrales and nasales.

The nervus oculo-motorius (S) gives off in the muscular cone
the ramus superior (a), passing to the levator palpebrse superior
and the rectus superior, and l /r/ .8 further forward divides it-
self into two twigs, of which the inner proceeds to the muscu-
lus rectus internus (c), and the outer (b) again divides to send
a branch to the rectus inferior, and the other to the obliquus
inferior.

The latter lies on the outer side of the rectus inferior, and
gives off, soon after its origin, a branch about \'" long and
\'" in thickness, the radix brevis ganglii ciliaris (W), which,
after passing over the nervus abducens, enters the ciliary
ganglion.

Here, to the outer side, and partly over the short root, and
also over the ramus inferior oculo-motorii, are the arteria oph-
thalmica and the nervus opticus.

Sometimes twigs from the oculo-motorius are sent to the
rectus externus and the obliquus superior, and frequently



OF THE HUMAN EYE. 137

there is a communication between the ramus superior oculo-mo-
torii and the nervus naso-ciliaris.

There proceeds from the nervus sympathicus, out of the
plexus caroticus, in the sinus cavernosus, a thin filament,
which passes through the middle division of the fissura orbi-
talis superior, called radix media or trophica ganglii ciliaris (r),
and unites with the ciliary ganglion.

There are certain anomalous connections with the ganglion
ciliare, such as the radix inferior longa, which comes from the
nervus naso-ciliares, beyond the optic nerve, or from a free
ciliary nerve, which lies beneath the nervus options, and forms
a nerve ring, by connecting with that part of the nervus naso-
ciliares which rests on the optic nerve, and which passes
through the nervus opticus. Again, a root of the nervus
lacrymalis passes to the radix longa. Another anomaly has
been noticed : the origin of the radix longa from the nervus
abducens.

Out of the ganglion ciliare there proceed two nerve fasciculi,
an inner thicker (m), and an outer and thinner (I) (Budge,
Pilz). The former again divides into an inner and outer fas-
cicule. From the inner part of the outer fascicule a nerve
proceeds (n), which runs beneath the optic nerve, and connects
itself with the nervus ciliaris longus internus, from the naso-
ciliaris (x), at which point (p) Faesebeck asserts to have found
a ganglion ciliare internum.

This has, however, been denied by Hyrtl and Budge, and
the sum of the matter is, that both nerves are in contact, and
from this union a twig proceeds beneath the nervus opticus
outward, which penetrates the sclerotica at some distance from
the optic nerve ; and two twigs, which enter the sclerotica
behind the optic nerve, and which have between them the
arteria ciliaris longa interna ( W). The second nerve from the
inner part of the inner fascicule (y), lies close to the outer side
of the nervus opticus, and divides into a number of branches,
' part of which proceed to the bloodvessels, and others are lost
in the fatty tissue. One of these branches (z) passes beneath



138 THE ANATOMY AND HISTOLOGY

the nervus opticus, and unites with the branch passing out-
ward that was first described. From the outer part of the
inner fascicule 4 to 5 twigs originate, all of which penetrate
the sclerotica close to the optic nerve, with the exception of
one twig, which runs some distance below the rectus superior
to the rectus internus, and sends off vascular twigs, which also
enter the sclerotica near the entrance of the optic nerve.

The outer fascicule divides into three filaments, one of which,
far inward, ascends over the optic nerve, whilst the other two
pierce the sclerotica more outwardly. They send off vascular
twigs, one of which, it is said (Hirzel and Tiedemann), pene-
trates the nervus opticus and passes to the arteria centralis
retinae. Besides the nerves forming the ganglion ciliare, the
sixth pair of cerebral nerves enter the cavity of the eye-muscle
cone. This nervus abducens enters the rectus externus at its
origin in the tendinous ring, and passes to the inner surface of
the muscle.

Through the upper division of the fissura orbitalis superior,
formed by the tendinous ring, three nerves enter the orbit,
the nervus trochlearis, or fourth pair of cerebral nerves, and
two branches of the first ramus of the nervus trigemini, the
nervus lacrymalis and the nervus frontalis.

The nervus trochlearis (Fig. 63, D), at the posterior part of
the hollow muscle cone, lies on the outer side of the nervus
frontalis, but runs over it in its course forward, passes over
the upper surface of the levator palpebrae muscle, to the upper
surface of the musculus obliquus superior.

The nervus lacrymalis (e) passes into the orbit through the
outer angle of the fissura orbitalis superior, further outward
than the nervus trochlearis and frontalis, through a peculiar
small canal in the upper division of this fissure, and runs along
the upper border of the musculus rectus externus, on the wall
of the orbit, to the outer eye-angle, where it terminates in the
rami conjuncti vales palpebrales and cutanei externi. In its
course it anastomoses with the nervus subcutaneus malse,



OF THE HUMAN EYE. 139

the second branch of the trigeminus, and also sends branches
to the lachrymal gland.

The nervus frontalis (Fig. 63, /) runs along between the roof
of the orbit and the upper surface! of the musculus levator pal-
pebrse superioris to the foramen supraorbitale, to pass into the
forehead ; as it emerges from the forehead, it gives off a small
branch, the nervus supra-trochlearis, which passes through
the suspensory band of the trochlea to the eyelid ; it forms an
anastomosis with the nervus infra-trochlearis. '

It will be observed that all the nerves of the orbit described


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